The prior art is replete with numerous examples of reclining and/or articulated chairs and the like. Some of these chairs are motorized (see, for example, U.S. Pat. Nos. 3,719,391 and 4,004,763), while others are of a non-motorized variety (see, for example, U.S. Pat. Nos. 2,497,395; 3,856,346; 4,195,878; 4,547,017 and 4,613,186).
With respect to the motorized reclining chairs, the one disclosed in U.S. Pat. No. 3,719,391 is adapted for use as a dental chair and is provided with slidable seat and backrest frames which move in a converging manner in response to a lowering of the backrest, thereby avoiding movement of the patient's body on the seat and the backrest as the chair is moved between a sitting position and a reclined position. A complicated and therefore expensive drive mechanism, which includes an electrically-driven worm screw, is employed to effect the desired movement of the seat and backrest frames.
Turning now to the non-motorized reclining chairs, the one disclosed in U.S. Pat. No. 4,547,017 is designed to maintain a user in a position which is very close to equilibrium in all relative positions of the backrest and the seat. As a result, the user may modify the position of the chair without any need to exert an appreciable force on its backrest and/or seat. The armrest and the backrest of the chair are provided with grooves sized and shaped to receive pins or rollers which cooperate with the grooves to control the relative movement of the backrest and the seat as the chair is moved between an upright position and a reclined position.